1. Field of the Invention
This invention relates generally to medical devices and procedures, and more particularly to a method and system of deploying a stent graft in a vascular system.
2. Description of the Related Art
Prostheses for implantation in blood vessels or other similar organs of the living body are, in general, well known in the medical art. For example, prosthetic vascular grafts formed of biocompatible materials (e.g., Dacron or expanded, porous polytetrafluoroethylene (PTFE) tubing) have been employed to replace or bypass damaged or occluded natural blood vessels.
A graft material supported by a framework is known as a stent graft or endoluminal graft. In general, the use of stent grafts for treatment or isolation of vascular aneurysms and vessel walls which have been thinned or thickened by disease (endoluminal repair or exclusion) is well known.
Many stent grafts, are “self-expanding”, i.e., inserted into the vascular system in a compressed or contracted state, and permitted to expand upon removal of a restraint. Self-expanding stent grafts typically employ a wire or tube configured (e.g., bent or cut) to provide an outward radial force and employ a suitable elastic material such as stainless steel or nitinol (nickel-titanium). Nitinol may additionally be conditioned to utilize shape memory properties of the alloy.
The self-expanding stent graft is typically configured in a tubular shape and sized for implantation to have a slightly greater diameter than the diameter of the blood vessel in which the stent graft is intended to be used. In general, rather than providing a repair using open surgery which is traumatic and highly invasive, stents and stent grafts are typically deployed through a less invasive intraluminal delivery, i.e., cutting through the skin to access a lumen or vasculature or percutaneously via successive dilatation, at a convenient (and less traumatic) entry point, and routing a catheter delivery system containing a stent graft through the lumen to the site where the stent graft is to be deployed.
Intraluminal deployment in one example is effected using a delivery catheter with coaxial inner tube, sometimes called the plunger, and outer tube, sometimes called the sheath, arranged for relative axial movement. The stent graft is compressed and disposed within the distal end of the sheath in front of the inner tube.
The catheter is then maneuvered, typically routed though a lumen (e.g., vessel), until the end of the catheter (and the stent graft) is positioned in the vicinity of the intended treatment site. The inner tube is then held stationary while the sheath of the delivery catheter is withdrawn. The inner tube contains a stent stop which prevents the stent graft from moving back as the sheath is withdrawn.
As the sheath is withdrawn, the stent graft is gradually exposed from a proximal end to a distal end of the stent graft, the exposed portion of the stent graft radially expands so that at least a portion of the expanded portion is in substantially conforming surface contact with a portion of the interior of the lumen, e.g., blood vessel wall.
The proximal end of the stent graft is the end closest to the heart by way of blood flow path whereas the distal end is the end furthest away from the heart by way of blood flow path during deployment. In contrast and of note, the distal end of the catheter is usually identified to the end that is farthest from the operator (handle) while the proximal end of the catheter is the end nearest the operator (handle). For purposes of clarity of discussion, as used herein, the distal end of the catheter is the end that is farthest from the operator (the end furthest from the handle) while the distal end of the stent graft is the end nearest the operator (the end nearest the handle), i.e., the distal end of the catheter and the proximal end of the stent graft are the ends furthest from the handle while the proximal end of the catheter and the distal end of the stent graft are the ends nearest the handle. However, those of skill in the art will understand that depending upon the access location, the stent graft and delivery system description may be consistent or opposite in actual usage.